File:Structure of an Army Heavy Corps.gif

Figure A-4. Structure of an Army Heavy Corps

The corps, commanded by a lieutenant general, is the Army's largest tactical formation. A corps commands and supports two to five divisions and an armored cavalry regiment. Slight variations exist between a heavy corps (such as III Corps) and a light corps (such as XVIII Airborne Corps), but those differences are generally minor, and all corps are capable of including heavy or light subordinate divisions.

The largest single element of the corps structure (other than the subordinate divisions) is the corps support command, which includes a corps support group (CSG) for the corps itself, one CSG for each subordinate division, and a medical brigade. CSGs are multifunction logistics commands with a variety of subordinate logistics battalions.

Most of the rest of the corps's structure consists of combat-support brigades and groups, each with a variable number of subordinate battalions depending on the number of subordinate divisions assigned to the corps and on operational factors. The combat-support brigades include engineer, chemical, military police, military intelligence, signals, personnel, finance, and civil affairs brigades.

The corps includes the bulk of the Army's artillery firepower, with a corps artillery commanding a variable number of artillery brigades. Each corps has an artillery brigade for the corps itself and one or two artillery brigades for each subordinate division. In addition, a corps contains an aviation brigade, an air-defense brigade, and a psychological operations battalion, which are unlikely to vary in size.

According to Army doctrine, separate brigades are normally attached to a corps. However, in recent rotations for Operation Iraqi Freedom, the Army has opted to attach separate brigades to divisions.